Heredity and sex . in nature associated with onesex alone. It has long been recognized in mammals and birdsthat there is a close connection between sexual maturityand the full development of the secondary sexual char-acters. This relation suggests some intimate correla-tion between the two. It has been shown, in fact, insome mammals at least, that the development of thesecondary sexual characters does not take place, orthat they develop imperfectly, if the sex glands areremoved. It may appear, therefore, that we are deal-ing here with a purely physiological process, and that 132 THE EFFECTS OF
Heredity and sex . in nature associated with onesex alone. It has long been recognized in mammals and birdsthat there is a close connection between sexual maturityand the full development of the secondary sexual char-acters. This relation suggests some intimate correla-tion between the two. It has been shown, in fact, insome mammals at least, that the development of thesecondary sexual characters does not take place, orthat they develop imperfectly, if the sex glands areremoved. It may appear, therefore, that we are deal-ing here with a purely physiological process, and that 132 THE EFFECTS OF CASTRATION 133 the development of these structures and colors is a by-product of sex itself, and calls for no further explana-tion. But the question cannot be so hastily can best be shown by taking up at once the ma-terial at hand. OPERATIONS ON MAMMALS In the deer, the facts are very simple. If the veryyoung male is castrated before the knobs of the antlershave appeared, the antlers never Fig. 67. — Merino; male (horned) and female (hornless). If the operation is performed at the time when theantlers have already begun to develop, incompletedevelopment takes place. The antlers remain coveredby the velvet and are never thrown off. They are calledperuke antlers. If the adult stag is castrated whenthe horns are fully developed, they are precociously 134 HEREDITY AND SEX dropped, and are replaced, if at all, by imperfect ant-lers, and these are never renewed. These facts make it clear that there is an intimaterelation between the orderly sequence of developmentof the horns in the deer and the presence of the malesexual glands. In the case of sheep, the evidence is more we have carefully planned experiments in whichboth sexes have been studied; and there are breeding
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjectsex, bookyear1913
